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Megapodiidaemegapodes(Also: mound-builders or megapodes)

By Laura Howard

Diversity

Megapodiidae comprises six genera and 19 species. Taxa of Megapapodiidae are commonly referred to as scrub fowl (Macrocephalon, Megapodius, Eulipoa); brush-turkeys (Alectura, Aepypodius, Talegalla), or mallee fowl (Leipoa). Megapodes are chicken-like birds with notably large feet. Instead of using body heat to directly incubate eggs, megapodes passively incubate eggs. Megapodes are sometimes referred to as mound builders because of their habit of burying their eggs under mounds of decaying vegetation. Some megapodes place their eggs in shallow pits or burrows to be warmed geothermally or with sun-warmed sand. Upon hatching, the feathered chicks, dig out from under the mound (or emerge from the burrow) and are able to forage, walk, run and fly. Parental care of emergent chicks has not been observed. (Campbell and Lack, 1985; Dyke, et al., 2003; Sibley and Ahlquist, 1990)

Geographic Range

Megapodes are found in the Oriental and Australian regions east of Wallace's line. They range from Australia, New Guinea (and surrounding islands) through eastern Indonesia to the Philippines. (Jones, et al., 1995; Payne, 2000)

Habitat

Megapodes inhabit a diversity of forest types (wet, dry, humid, swamp, gallery, monsoon) in lowland and highland regions. Some species occupy scrub forests, urban areas, and semi-arid habitats. (Campbell and Lack, 1985; Jones, et al., 1995)

  • Other Habitat Features
  • urban

Physical Description

Megapodes are medium to large chicken-like birds with large feet. Adult body measurements are variable, from 50 cm to 70 cm in length and 275 g to 2950 g in weight. Megapodes are generally brown to black in color. Some species have a prominent head casque, wattles or bare heads and necks with brightly colored skin. Most species are sexually monomorphic in appearance, although one is dimorphic in size (females smaller), coloration (females less brightly colored) and wattles (female wattles absent). Upon hatching, chicks are covered with brown or buffy feathers (not down). Weight at hatching is variable, perhaps ranging from 80 g to 173 g. (Campbell and Lack, 1985; Jones, et al., 1995)

  • Sexual Dimorphism
  • sexes alike
  • sexes colored or patterned differently
  • male more colorful
  • ornamentation

Reproduction

Most megapodes are described as monogamous, although some species probably exhibit polygynandry. Monogamous pairs appear to form social bonds that may continue outside of the breeding season. Males generally compete for and defend incubation sites or females. Some species congregate regularly to roost. Species that use clumped geothermal incubation sites may aggregate in large numbers (over 50,000) onto communal incubation sites.

Megapodius spp., Eulipoa wallacei, and perhaps Talegalla are thought to exhibit female-defense monogamy. Males appear to defend a single female. The process of mate selection and pair formation is not known. The pairs stay in close proximity, exhibit behavioral synchrony, and locate and maintain incubation sites together. Pairs avoid other pairs through loud vocalizations.

Mallee fowl are considered to exhibit resource-defense monogamy. Pair bonds are evident for part of the breeding season. Males alone compete aggressively for mound sites. During construction of the incubation mound a pair works together, but once egg laying begins the male and female appear to become independent of one another.

Brush-turkeys (Aepydius) are thought to exhibit resource-defense polygynandry. Males defend incubation sites. The sexes interact only when females visit incubation mounds to copulate and to lay eggs. Females may lay eggs for multiple males. Males alone compete for, maintain and defend incubation mounds. Males and females may copulate with multiple mates. (Campbell and Lack, 1985; Jones, et al., 1995; Payne, 2000)

The length of the breeding season is variable. The beginning of the construction of incubation sites appears to be related to local climactic conditions. In some species the beginning of incubation site construction coincides with the onset of the rainy season and in others it coincides with the onset of the dry season.

Females may lay from 3 to 35 eggs over the course of the breeding season. The egg-laying interval may be 2 to 13 days and may occur over periods ranging from 2 to 4 months. Megapode eggs are generally white or creamy in color. Eggs are large and variable in size depending on species (weights range from 75 to 230 g).

Incubation period appears to be dependent on the temperature in the mound or burrow. The average duration may range from 44 to 77 days. Megapode chicks are precocial. Chicks may hatch from 20 cm to 1 m below the surface of the mound. The time it takes for chicks to reach the surface is variable, but may range from 2 to 60 hours. Digging out of the mound is thought to entail chicks lying on their backs and scraping the material with their feet, then compressing the falling material with their backs. Chicks dig out from the mound without direct parental assistance. Upon emergence chicks have functional flight feathers, can walk and run, and commence foraging independently. Little is known about the foraging abilities of newly emergent chicks. No parental care of emergent chicks has been observed. Age of maturity is not well known, but may be achieved in 1 to 3 years. (Campbell and Lack, 1985; Jones, et al., 1995)

Megapode chicks are precocial. No parental care of chicks has been observed. However, adult males spend a prolonged period caring for eggs by defending and maintaining incubation sites, and monitoring incubation temperatures. (Campbell and Lack, 1985; Jones, et al., 1995)

Lifespan/Longevity

No specific information was found concerning longevity for this family.

Behavior

Megapodes are mainly terrestrial ground dwelling birds that move about mostly by walking. Some species fly frequently while others fly mainly to roost in trees or to escape predation. They are sedentary and generally do not migrate. Brush turkeys and mallee fowl are largely solitary whereas other species appear to live in pairs. Some megapodes congregate and roost in large numbers.

Mound construction entails digging and scraping with the feet and toes, and the collection and mixing of organic materials. Construction of the incubation mound may be done by the male alone or jointly by the mated pair. Male and female megapodes have been observed to monitor the temperature of the incubation chamber. The head is inserted into a previously excavated chamber that leads to the core of the mound. Females generally check the temperature of a mound just prior to laying. Males often monitor temperature during the incubation period.

Intra- and inter-sexual conflicts occur in conjunction with competition for resources (incubation sites, females, food items). Aggressive interactions include chases, pecks, threat displays and wing-blows. Submission appears to include a drawing in of the neck and movement away from dominant bird. Chicks appear to avoid one another during the first weeks after emergence. If chicks do meet, the interactions are often agonistic. (Jones, et al., 1995)

Communication and Perception

Brush turkeys have colorful head and neck skin, inflatable neck sacs, and head combs that are likely used in visual signaling. Coloration of these parts becomes more pronounced during the breeding season and during copulatory activities. The combs and neck sacs of males become enlarged during the breeding season.

Megapode vocalizations generally entail clucking, crowing or booming. Clucking, squawking or grunting may be used as short distance intraspecific contact calls. Crowing is generally a loud repetitive call that may be heard day or night. Crowing carries long distances and may function as territorial cries or as contact calls between mated pairs. Pairs may duet by crowing. Booming is deep and resonant. Booming may occur during male-male interactions or when a male is alone at his incubation site. The function of booming may be as a social signal between males or as an advertisement to females. (Campbell and Lack, 1985; Jones, et al., 1995)

  • Other Communication Modes
  • duets

Food Habits

Megapodes are omnivores, known to eat plant material, invertebrates and small vertebrates. The plant material they eat includes: seeds, fruits, berries, various sprouts/shoots, foliage and flowers. Invertebrates consumed include: termites, ants, cockroaches, grasshoppers, dragonflies, spiders, wasps, centipedes, snails, worms, small crabs. Small vertebrates include frogs and small lizards. (Campbell and Lack, 1985; Jones, et al., 1995)

Predation

Known predators of megapodes include omnivorous and carnivorous mammals and include: red foxes (Vulpes vulpes), cats (Felidae), leopards (Panthera), civet-cats (Viverridae), feral dogs (Canis lupus familiaris), snakes (Serpentes) and raptors (Falconiformes). (Jones, et al., 1995)

Ecosystem Roles

Megapodes may influence the local ecosystem by dispersing seeds or altering the habitat via construction of incubation mounds/burrows.

  • Ecosystem Impact
  • disperses seeds
  • creates habitat

Economic Importance for Humans: Positive

Humans collect the eggs and hunt the adults of many megapode species. These items are either consumed directly or sold in local markets. (Campbell and Lack, 1985; Jones, et al., 1995)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

Megapodes may damage home gardens as a result of mound construction activities. Plantations and farms suffer losses of shoots and seedlings due to megapode foraging activities. (Campbell and Lack, 1985; Jones, et al., 1995)

  • Negative Impacts
  • crop pest
  • household pest

Conservation Status

Ten species of megapodes are included in the IUCN Red List of Threatened Species. One species, nevafou megapode (Megapodius pritchardii), is listed as 'Critically Endangered'. Two species, Maleo megapode (Macrocephalon maleo) and Micronesian megapode (Megapodius laperouse), are listed as 'Endangered'. Seven species are listed as 'Vulnerable'. Major threats include habitat loss, egg collection and introduced species. (Collar, et al., 1994; IUCN 2003, 2003)

  • IUCN Red List [Link]
    Not Evaluated

Contributors

Laura Howard (author), Animal Diversity Web, Alaine Camfield (editor), Animal Diversity Web.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

duets

to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

frugivore

an animal that mainly eats fruit

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

polymorphic

"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

young precocial

young are relatively well-developed when born

References

Campbell, B., E. Lack. 1985. A Dictionary of Birds. Vermillion: Buteo Books.

Collar, N., M. Crosby, A. Stattersfield. 1994. Birds to Watch 2, The World List of Threatened Birds. Washington, D.C: Smithsonian Institution Press.

Dyke, G., B. Gulas, T. Crowe. 2003. Suprageneric relationships of galliform birds (Aves, Galliformes): a cladistic analysis of morphological characters. Zoological Journal of the Linnean Society, 137: 227-244.

Haaramo, M. 2003. "Mikko's Phylogeny Archives, Field Museum of Natural History, Helsinki, Finland" (On-line). Accessed March 06, 2004 at http://www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma/Chordata/Archosauria/Aves/Galliformes/Galliformes.htm.

IUCN 2003, 2003. "2003 IUCN Red List of Threatened Species" (On-line). Accessed March 09, 2004 at http://www.redlist.org.

Jones, D., R. Dekker, C. Roselaar. 1995. The Megapodes. New York: Oxford University Press Inc.

Livezey, B., R. Zusi. 2001. Higher-order phylogenetics of modern Aves based on comparative anatomy. Netherlands Journal of Zoology, 51(2): 179-205.

Monroe, B., C. Sibley. 1993. A World Checklist of Birds. Ann Arbor: Edwards Brothers Inc.

Payne, R. 2000. "Birds of the World, Biology 532, Recent Families, Birds of the World." (On-line). Accessed March 16, 2004 at http://www.ummz.lsa.umich.edu/birds/birddivresources/families.html.

Sibley, C., J. Ahlquist. 1990. Phylogeny and Classification of Birds, A Study in Molecular Evolution. New Haven: Yale University Press.

Sorenson, M., E. Oneal, J. Garcia-Moreno, D. Mindell. 2003. More taxa, more characters: the Hoatzin problem is still unresolved. Molecular Biology and Evolution, 20(9): 1484-1499.

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